Synthesis of 21-thia and 21-oxaporphyrin building blocks and boron-dipyrrin appended systems

Article abstract of DOI:10.1016/S0040-4020(02)00482-9

A series of 21-thia and 21-oxaporphyrin building blocks bearing iodo-, ethynyl-and aldehyde functional groups were synthesized and characterized. These porphyrins are ideal building blocks for the construction of unsymmetrical porphyrin arrays containing

Full text of DOI:10.1016/S0040-4020(02)00482-9

TETRAHEDRON
Pergamon
Tetrahedron 58 72002) 5347±5356
Synthesis of 21-thia and 21-oxaporphyrin building blocks and
boron±dipyrrin appended systems
D. Kumaresan, Neeraj Agarwal, Iti Gupta and M. Ravikanthp
Department of Chemistry, Indian Institute of Technology, Powai, Mumbai 400076, India
Received 17 January 2002; revised 9 April 2002; accepted 2 May 2002
AbstractÐA series of 21-thia and 21-oxaporphyrin building blocks bearing iodo-, ethynyl-and aldehyde functional groups were synthesized
and characterized. These porphyrins are ideal building blocks for the construction of unsymmetrical porphyrin arrays containing two
dissimilar porphyrin cores. The building blocks were used to construct boron±dipyrrin appended core-modi®ed porphyrin systems under
mild palladium coupling conditions. A preliminary steady state ¯uorescence measurements suggested that boron±dipyrrin unit transfers the
energy to both 21-oxaporphyrin and 21-thiaporphyrin and the ef®ciency depends on the orientation of the boron±dipyrrin units and the core
structure of the porphyrin. q 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction
tional groups and their application towards the construction
of energy donor appended 21-thia and 21-oxaporphyrin
systems. A boron±dipyrrin 7BDPY) unit was used as energy
donor. A preliminary steady state ¯uorescence study indi-
cates that there is an energy transfer from boron±dipyrrin
units to 21-oxaporphyrin and 21-thiaporphyrin and the ef®-
ciency of energy transfer depends on the orientation and
distance of boron±dipyrrin and porphyrin units as well as
the structure of the porphyrin core.
Core-modi®ed porphyrins resulting from the replacement of
pyrrole with heterocycles such as thiophene, furan, seleno-
phene and tellurophene have received less attention inspite
of their novel properties such as stabilization of metals in
unusual oxidation states.1 Most of the studies on core modi-
®ed chemistry has been directed towards the synthesis and
stabilization of metals such as copper, nickel and rhodium in
unusual oxidation states.2 For example, it has been shown
that 5,10,15,20-tetraphenyl-21-thiaporphyrin 7N3S core) can
stabilize copper in 11 oxidation state which is not possible
with a normal 5,10,15,20-tetraphenyl porphyrin 7N4 core).
Though in recent times, few papers have appeared on new
21-thiaporphyrin systems, the reports on 21-oxaporphyrin
7N3O) core are also still rare.3 We have been interested in
synthesis and chemistry of new core modi®ed porphyrins to
use them for biorganic and materials chemistry applications
and in this direction, we have recently reported the synthesis
of an unsymmetrical porphyrin pentamer containing one
central dithiaporphyrin 7N2S2 core) which was connected
covalently by diaryl ethyne bridges to peripheral normal
porphyrin systems.4 We demonstrated an ef®cient energy
transfer from peripheral N4 systems to the central N2S2
system. We have also reported the synthesis of b-substituted
21-thiaporphyrins5a and water-soluble 21-oxaporphyrins.5b
In continuation of our study on core modi®ed porphyrin
chemistry, in this paper, we report the synthesis and char-
acterization of a series of 21-thia and 21-oxaporphyrin
building blocks6 bearing iodo-, ethyne- and aldehyde func-
2. Results and discussion
2.1. 21-Thiaporphyrin building blocks
The required thiophene diol, 2,5-bis7phenyl hydroxy-
methyl)thiophene was prepared in 65% yield by the double
alkylation of the dianion of thiophene with benzaldehyde.7
The other precursors such as 3- or 4-[2-7trimethylsilyl)-
ethynyl]benzaldehyde,8a 3- or 4-iodobenzaldehyde8b and
2-75,5-dimethyl-1,3-dioxacyclohex-2-yl) benzaldehyde8c
were prepared by following literature procedures. The
condensation of 1 equiv. of 2,5-bis7phenyl hydroxymethyl)
thiophene with 2 equiv. of appropriate aldehyde and
3 equiv. of pyrrole gave a crude porphyrin mixture. The tlc
analysis clearly showed the formation of three porphyrins. It
is interesting to note that the above condensation resulted in
the formation of three porphyrins with three different
porphyrins cores: N2S2, N3S and N4. For example, as
shown in the Scheme 1, the condensation of 2,5-bis7phenyl
hydroxymethyl)thiophene, 4-iodobenzaldehyde and pyrrole
gave three porphyrins: 5,10,15,20-tetraphenyl-21,23-
dithiaporphyrin 7N2S2, 2%), a desired 5,10-diphenyl-
15,20-bis74-iodophenyl)21-thiaporphyrin, 5 7N3S, 17%)
and 5,10,15,20-tetra74-iodophenyl)porphyrin 7N4, 3%).
Keywords: porphyrin building blocks; core modi®ed porphyrins; boron±
dipyrrin; energy transfer.
Corresponding author. Fax: 191-22-576-7152;
e-mail: ravikanth@chem.iitb.ernet.in
p
0040±4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020702)00482-9

5348
D. Kumaresan et al. / Tetrahedron 58 %2002) 5347±5356
Scheme 1. Synthetic scheme of 21-thiaporphyrin building block, 5.
Absorption spectroscopy is a very good tool for identifying
the three porphyrins since the absorption bands 7both soret
and Q-bands) of all three porphyrins are very different from
each other. The bands are red shifted as core changes from
N4 to N3S to N2S2. Thus absorption spectroscopy is a fast
and easy way to identify the required 21-thiaporphyrin
building blocks. The mixture of three porphyrins was sepa-
rated by silica gel column chromatography. Generally, the
dithiaporphyrin moves as the ®rst band followed by the
desired 21-thiaporphyrin building block as the second
band. The building blocks with iodo- and CCTMS-func-
tional groups were obtained in 10±17% yields 7Table 1).
The deprotection of the trimethyl silyl group of 1 and 3 was
carried out by treating with K2CO3 in THF±methanol 73:1)
giving 2 and 4, respectively, in 80% yield.8a The building
block with formyl functional group 8 was prepared by
deprotecting 7 with tri¯uoroacetic acid in the presence of
dilute H2SO4. 7 was prepared in 3% yield by condensing
2,5-bis7phenyl hydroxymethyl) thiophene with 2-75,5-
dimethyl-1,3-dioxacyclohex-2-yl)
benzaldehyde
and
pyrrole in CHCl3 using TFA as catalyst. Use of
BF3´O7Et)2 as catalyst in this reaction gave very small
amounts of porphyrin.
Table 1. 21-Thiaporphyrin building blocks
All 21-thiaporphyrin building blocks with iodo-, ethynyl-
and aldehyde groups were characterized by 1H NMR,
mass spectroscopy, C, H, N analysis, absorption and ¯uores-
cence spectroscopy. The 1H NMR spectrum of 8 is shown in
Fig. 17a). In all 21-thiaporphyrin building blocks, the thio-
phene protons appeared as singlet and three pyrroles
appeared as three separate signals. This indicates the low
symmetric nature of the porphyrin building blocks. The
FAB-MS spectra showed a molecular ion peak con®rming
the product. Absorption spectra exhibited one Soret and four
Q-bands and the peak positions were in close match with
5,10,15,20-tetraphenyl-21-thiaporphyrin. C, H, N analyses
was also in agreement with the expected porphyrin building
blocks.
Porphyrin
Ar
Yield 7%)
1
15
2.2. 21-Oxaporphyrin building blocks
3
14
2,5-Bis7phenyl hydroxymethyl)furan was synthesized simi-
larly to the synthesis of 2,5-bis7phenyl hydroxymethyl)thio-
phene by the double alkylation of the dianion of furan with
benzaldehyde.1b The condensation of 2,5-bis7phenyl hydro-
xymethyl)furan with corresponding aldehyde and pyrrole
gave a mixture of three porphyrins: 5,10,15,20-tetra-
phenyl-21,23-dioxoporphyrin 7N2O2), the required 21-
oxaporphyrin with ±I, or ±CCTMS groups 7N3S) and tetra-
phenyl porphyrin with ±I or ±CCTMS groups 7N4). The 21-
oxaporphyrin building blocks were obtained in 10±15%
5
6
17
11
7
3

D. Kumaresan et al. / Tetrahedron 58 %2002) 5347±5356
5349
1
Figure 1. H NMR spectra of: 7a) 8 and 7b) 12 recorded in CDCl3.
Table 2. 21-Oxaporphyrin building blocks
yields 7Table 2). The deprotection of the trimethyl silyl
group in 9 and 11 was carried out in THF±methanol in
the presence of K2CO3 gave 10 and 12, respectively,8a
Porphyrin building block 15 was prepared in relatively
low yield using TFA as catalyst. The deprotection of 15
with tri¯uoroacetic acid in the presence of dilute H2SO4
gave 16 in 55% yield. All building blocks were character-
1
ized using spectroscopic techniques. The H NMR spectra
7Fig. 17b)) show a singlet for furan and the three pyrroles
appear as two or three signals indicating the low symmetry
nature of porphyrins. FAB-MS and C, H, N analyses further
con®rmed the products. Absorption spectra of the other two
side products 7N2O2 and N4 porphyrins) were very different
from the required porphyrin and hence useful in identifying
the right compound.
Porphyrin
Ar
Yield 7%)
9
15
2.3. Boron±dipyrrin appended 21-thia and 21-
oxaporphyrins
11
10
The porphyrin building blocks with ±I, ±CCH and ±CHO
functional groups are very useful for preparing series of
unsymmetrical porphyrin arrays and donor appended
porphyrin systems.6 Thus we used the core modi®ed
porphyrin building blocks to synthesize boron±dipyrrin
appended porphyrin systems 17 and 18 as outlined in
Scheme 2. Coupling of 2 with N,N-di¯uoroboryl-1,9-
dimethyl-5-74-iodophenyl)-dipyrrin 7BDPY-I) in toluene/
triethylamine at 358C in the presence of Pd27dba)3 and
13
14
14
11
15
5

5350
D. Kumaresan et al. / Tetrahedron 58 %2002) 5347±5356
Scheme 2. Synthetic scheme for 17 and 18.
AsPh3 gave 17 in 28% yield and coupling of 12 with BDPY-
I under same conditions gave 18 in 17% yield.9 Both 17 and
18 were characterized using 1H NMR, FAB-MS, absorption
and emission spectroscopies. 1H NMR spectra of 17 and 18
are shown in Fig. 2. In both cases, the pyrroles of the
porphyrin ring appear as three separate signals. The pyrrole
protons of BDPY unit appear up®eld as two doublets in 17
and as two multiplets in 18. The b-thiophene in 17 and b-
furan in 18 appear as singlets. The FAB-MS showed a mole-
cular ion peak con®rming that the porphyrin systems are
appended with two BDPY units. The absorption spectra
7Fig. 3) show four bands; one Soret and three Q-bands.
The peak at 515 nm which is mainly due to BDPY units10
is much larger in intensity than the other two Q-bands which
are mainly due to the porphyrin ring. The emission spectra
recorded at 485 nm for both 17 and 18 are shown in Fig. 4.
As evident from Fig. 4, both 17 and 18 excited at 485 nm
where BDPY absorbs predominantly resulted in emission
from both BDPY and porphyrin units. Though in the case
of 18, the strong emission was from 21-oxoporphyrin unit
with a comparatively weak emission from BDPY unit indi-
cating a clear transfer of energy from BDPY unit to 21-
oxoporphyrin unit, the quantum yield data suggest that the
energy transfer from boron±dipyrrin to porphyrin unit was
also evident in 17. The quantum yield of BDPY unit in both
17 7fˆ0.0306) and 18 7fˆ0.0198) was decreased from the
free BDPY 7fˆ0.18) supporting the above observation.10
The ef®ciency of energy transfer appears to be greater in 18
than 17. However, it is dif®cult to compare these two
systems since the distance and the orientation of BDPY
units with the porphyrin unit are different in 17 and 18. In
case of 17, the distance between the boron±dipyrrin and
porphyrin is longer than 18 and the orientation of BDPY
units w.r.t porphyrin is also different. A detailed study of the
photodynamics of these systems taking the distance and
orientation of donor and acceptor into consideration would
help to understand the difference of energy transfer in 17
and 18.

D. Kumaresan et al. / Tetrahedron 58 %2002) 5347±5356
5351
1
Figure 2. H NMR spectra of: 7a) 17 and 7b) 18 recorded in CDCl3. 7p) indicates solvent and its impurity.
3. Conclusions
very easy to synthesize. Spectroscopic techniques like
absorption and ¯uorescence spectroscopy were suf®cient
to identify and isolate the core modi®ed building blocks in
reasonable yields. We have also shown the use of these core
modi®ed building blocks to synthesize energy donor
appended systems under mild palladium coupling condi-
tions. Much more extensive studies would be required to
understand the energy transfer dynamics in these systems.
In conclusion, we have prepared a series of 21-thia and 21-
oxaporphyrin building blocks bearing iodo-, ethyne- and
aldehyde functional groups. The cis-porphyrin building
blocks reported here are very dif®cult to make with N4
porphyrin systems. However, the core modi®ed porphyrin
building blocks with functional groups in cis fashion were
Figure 3. UV±Vis spectra 17 7Ð) and 18 7- - -) recorded in toluene.

5352
D. Kumaresan et al. / Tetrahedron 58 %2002) 5347±5356
Figure 4. Fluorescence spectra of 17 7Ð) and 18 7- - -) recorded in toluene at lexˆ515 nm.
The building blocks can also be used to synthesize unsym-
metrical porphyrin arrays containing core modi®ed porphyrin
and normal porphyrin which are ideal systems to understand
the electron and energy transfer reactions of photosynthesis.
The synthesis and study of such unsymmetrical porphyrin
arrays are presently under investigation in our laboratory.
under reduced pressure and crude solid was dissolved in
CHCl3. A dark powdered slurry was then prepared by
adding silica gel and dried. The powder was loaded on a
silica column and slow gravity elution with pet ether/
CH2Cl2 or CH2Cl2/CH3OH was started. The desired
porphyrin was the second band in all porphyrin building
block reactions. Absorption and ¯uorescence spectroscopy
were used to identify the required compound. The desired
porphyrin was rechromatographed in an identical manner
for ®nal puri®cation.
4. Experimental
4.1. General
4.2.1. 5,10-Diphenyl-15,20-bis {4-[2-/trimethylsilyl)-
ethynyl]phenyl}-21-thiaporphyrin /1). A solution of 2,5-
bis7hydroxymethyl)thiophene 7500 mg, 1.69 mmol), 4-[2-
1H NMR spectra were recorded on a varian 300 MHz using
tetramethylsilane as internal standard. Absorption and
¯uorescence spectra were obtained with Shimadzu-160
and Spex Fluoromax respectively. The FAB mass spectra
were recorded on a JEOL SX 102/DA-6000 mass spectro-
meter using Argon/Xenon as the FAB gas. Toluene, THF
and triethylamine were obtained from S.D Fine chemicals,
India, and dried by standard procedures before use. All
general chemicals were obtained from Qualigens, India.
Benzaldehyde and pyrrole were obtained from Lancaster.
Column chromatography was performed using 60±120
mesh silica obtained from Sisco Research Laboratories,
India. Size exclusion chromatography was performed using
Bio-Beads SX-1 in toluene obtained from Biorad, USA.
7trimethylsilyl)ethynyl]
benzaldehyde
7683 mg,
0.675 mmol) and pyrrole 7352 ml, 5.083 mmol) in 250 ml
CHCl3 were condensed in the presence of BF3´O7Et)2
7330 ml of 2.5 M stock solution, 3.3 mM). After 1 h, DDQ
7573 mg, 0.748 mmol) was added and stirred for 1 h. Chro-
matography with pet ether/CH2Cl2 71:1) gave the required
1
purple compound 7218 mg, 15%). H NMR 7CDCl3, d in
ppm) 22.76 7s, 1H, NH), 0.39 7s, 18H, CH3), 7.83 7m, 10H,
Ar), 8.15 7m, 4H, Ar), 8.26 7m, 4H, Ar), 8.57 7d, 2H,
Jˆ4 Hz, b-pyrrole), 8.70 7d, 2H, Jˆ4 Hz, b-pyrrole), 8.90
7d, 2H, Jˆ4 Hz, b-pyrrole), 9.76 7s, 2H, b-thiophene). FAB-
MS C54H45N3SSi2 calcd mass, 823.2. obsd. m/z 823. Anal.
calcd: C, 78.8; H, 5.50; N, 5.09. Found: C, 79.2; H, 5.42; N,
4.89. IR 7KBr, n 7cm21)) 3323, 3030, 2943, 2154, 705. UV±
Vis 7lmax 7nm), 1 7dm3 mol21 cm21)) 431 7272,000), 514
718760), 549 75900), 619 72360), 679 73840).
4.2. General method for the synthesis and puri®cation of
porphyrin building blocks /1, 3, 5, 6, 9, 11, 13 and 14)
Samples of 1 equiv. of 2,5-bis7phenyl hydroxymethyl)thio-
phene or -furan and 2 equiv. of appropriate aldehyde 73- or
4-substituted benzaldehyde with ±I, ±CCTMS groups) were
dissolved in CHCl3 under argon in a one neck round bottom
¯ask. After 10 min purging with argon, 3 equiv. of pyrrole
were added and BF3´O7Et)2 73.3 mM) was added to initiate
the condensation. The reaction mixture was stirred for 1 h
under an argon atmosphere. Then DDQ was added and stir-
ring was continued for an additional 1 h. The formation of
porphyrin7s) was veri®ed by absorption spectroscopy. The
tlc analysis of crude reaction mixture indicated the forma-
tion of three expected pophyrins. The solvent was removed
4.2.2. 5,10-Diphenyl-15,20-bis/4-ethynylphenyl)-21-thia-
porphyrin /2). Compound 1 766 mg, 0.0802 mmol) was
dissolved in 30 ml of THF and K2CO3 in CH3OH 7200 mg
in 10 ml of CH3OH) was added to it. The reaction mixture
was heated to re¯ux for 6 h. The deprotection of trimethyl
silyl group was followed by tlc. The solvent was removed
and the compound was puri®ed by silica gel column chro-
matography using CH2Cl2 gave 2 as a purple solid 753 mg,
80%). 1H NMR 7CDCl3, d in ppm) 22.75 7s, 1H, NH), 3.25
7s, 2H, CCH), 7.81 7m, 10H, Ar), 8.15 7m, 4H, Ar), 8.25 7m,
4H, Ar), 8.55 7d, 2H, Jˆ4 Hz, b-pyrrole), 8.69 7d, 2H,

D. Kumaresan et al. / Tetrahedron 58 %2002) 5347±5356
5353
Jˆ4 Hz, b-pyrrole), 8.91 7d, 2H, Jˆ4 Hz, b-pyrrole), 9.78
7s, 2H, b-thiophene). FAB-MS C48H29N3S calcd mass
679.2, obsd. m/z 679. Anal. calcd: C, 84.9; H, 4.30; N,
6.18. Found: C, 84.2; H, 4.14; N, 6.08. IR 7KBr, n
7cm21)) 3335, 3295, 2927, 2854, 2111, 702. UV±Vis
7lmax 7nm), 1 7dm3mol21 cm21)) 431 7321,800), 514
726,920), 548 77740), 619 73400), 679 75260).
4.2.6.
porphyrin /6). A solution of 2,5-bis7phenyl hydroxy-
methyl)thiophene 7100 mg, 0.337 mmol), 3-iodo-
5,10-Diphenyl-15,20-bis/3-iodophenyl)-21-thia-
benzaldehyde 7156 mg, 0.675 mmol) and pyrrole 770 ml,
1.013 mmol) in 50 ml of CH2Cl2 was treated with
BF3´O7Et)2 766 ml of 2.5 M stock solution, 3.3 mM). After
1 h, DDQ 7170 mg, 0.5066 mmol) was added and left the
reaction for stirring for 1 h in air. Chromatography with pet
ether/CH2Cl2 71:1) gave 6 as a purple solid 731 mg, 11%).
1H NMR 7CDCl3, d in ppm) 22.76 7s, 1H, NH), 7.48 7t, 4H,
Jˆ6.5 Hz, Ar), 7.82 7m, 6H, Ar), 8.13±8.33 7m, 6H, Ar),
8.61 7m, 4H12H, Ar1b-py), 8.72 7d, 2H, Jˆ4.5 Hz, b-pyr-
role), 8.96 7bs, 2H, b-pyrrole), 9.78 7s, 2H, b-thiophene).
FAB-MS C44H27N3SI2 calcd mass 883.0, obsd. m/z 884.
Anal. calcd: C, 59.8; H, 3.07; N, 4.77. Found: C, 60.4; H,
3.01; N, 4.48. IR 7KBr, n 7cm21)) 3328, 3052, 2927, 2848,
709. UV±Vis 7lmax 7nm), 1 7dm3 mol21 cm21)) 430
7420,000), 513 728,500), 547 76840), 618 73420), 678
74720).
4.2.3. 5,10-Diphenyl-15,20-bis {3-[2-/trimethylsilyl)-
ethynyl]phenyl}-21-thiaporphyrin /3). Samples of 2,5-
bis7phenyl hydroxymethyl)thiophene 7200 mg, 0.676
mmol), 3-[2-7trimethylsilyl)ethynyl] benzaldehyde 7273
mg, 1.35 mmol) and pyrrole 7140 ml, 2.027 mmol) in
100 ml CHCl3 were treated with BF3´O7Et)2 7132 ml of
2.5 M stock solution, 3.3 mM) under argon for 1 h. DDQ
7229 mg, 1.013 mmol) was added and stirring was con-
tinued for extra 1 h. Chromatography with pet ether/
1
CH2Cl2 73:1) afforded a purple solid 779 mg, 14%). H
NMR 7CDCl3, d in ppm) 22.76 7s, 1H, NH), 0.26 7s,
18H, CH3), 7.68 7t, 2H, Jˆ6.5 Hz, Ar), 7.79 7m, 6H, Ar),
7.89 7m, 2H, Ar), 8.13 7m, 2H, Ar), 8.22±8.28 7m, 4H, Ar),
8.33 7s, 2H, Ar), 8.58 7d, 2H, Jˆ4.5 Hz, b-pyrrole), 8.69 7d,
2H, Jˆ4.5 Hz, b-pyrrole), 8.92 7s, 2H, b-pyrrole), 9.76 7s,
2H, b-thiophene). FAB-MS C54H45N3SSi2 calcd mass
823.2, obsd. m/z 824. Anal. calcd: C, 78.8; H, 5.50; N,
5.09. Found: C, 78.1; H, 5.43; N, 4.91. UV±Vis 7lmax
7nm), 1 7dm3 mol21 cm21)) 430 7370,610), 514 733,052),
548 77636), 618 74165), 678 75688).
4.2.7. 5,10-Diphenyl-15,20-bis[4-/5,5-dimethyl-1,3-dioxa-
cyclohex-2-yl)phenyl]-21-thiaporphyrin /7). Samples of
2,5-bis 7phenyl hydroxymethyl)thiophene 7100 mg,
0.337 mmol),
4-75,5-dimethyl-1,3-dioxacyclohex-2-yl)-
benzladehyde 7165 mg, 0.749 mmol) and pyrrole 7100 ml,
1.441 mmol) were dissolved in 25 ml of CHCl3 and stirred
at room temperature under argon for 10 min. Tri¯uoroacetic
acid 7100 ml, 0.0013 mmol) was added to initiate the
condensation and the reaction mixture was stirred for 1 h
under argon atmosphere. DDQ 7100 mg, 0.441 mmol) was
then added and the reaction mixture was stirred for
additional 1 h in air. The solvent was removed in
vacuo and the crude compound was loaded on silica and
eluted with CH2Cl2. The desire compound was the
second band with CH2Cl2/diethyl ether 785:15). The solvent
was removed on a rotary evaporator to afford 7 as dark
4.2.4. 5,10-Diphenyl-15,20-bis/3-ethynylphenyl)-21-thia-
porphyrin /4). Compound 3 750 mg, 0.0607 mmol) in
10 ml dry THF was treated with K2CO3 784 mg,
0.607 mmol) in 3 ml of CH3OH at re¯ux temperature for
6 h. Chromatography on silica with CH2Cl2 gave 4 as a
1
purple solid 734 mg, 82%). H NMR 7CDCl3, d in ppm)
22.75 7s, 1H, NH), 3.16 7s, 2H, CCH), 7.71 7t, 2H,
Jˆ6.5 Hz, Ar), 7.81 7m, 6H, Ar), 7.92 7m, 2H, Ar), 8.22±
8.28 7m, 4H, Ar), 8.35 7s, 2H, Ar), 8.58 7d, 2H, Jˆ4.5 Hz,
b-pyrrole), 8.71 7d, 2H, Jˆ4.5 Hz, b-pyrrole), 8.92 7d, 2H,
Jˆ4.5 Hz, b-pyrrole), 9.77 7s, 2H, b-thiophene). FAB-MS
C48H29N3S calcd mass 679.2, obsd. m/z 680. Anal. calcd: C,
84.9; H, 4.30; N, 6.18. Found: C, 84.3; H, 4.21; N, 6.05.
UV±Vis 7lmax 7nm), 1 7dm3 mol21 cm21)) 430 7345,280),
514 731,872), 547 77380), 617 74070), 677 75457).
1
purple solid in 3% 78.7 mg) yield. H NMR 7CDCl3, d in
ppm) 22.75 7s, 1H, NH), 1.54 7s, 12H, CH3), 3.86 7d, 4H,
Jˆ6.6 Hz, CH2), 3.97 7d, 4H, Jˆ6.6 Hz, CH2), 5.76 7s, 2H,
CH), 7.79 7m, 6H, Ar), 7.90 7m, 4H, Ar), 8.21 7m, 8H, Ar),
8.59 7d, 2H, Jˆ2.4 Hz, b-py), 8.66 7d, 2H, Jˆ2.4 Hz,
b-pyrrole), 8.91 7m, 2H, b-pyrrole), 9.74 7s, 2H, b-thio-
phene). FAB-MS C56H49N3O4S calcd mass 860.1, obsd.
m/z 861. Anal. calcd: C, 78.2; H, 5.74; N, 4.88. Found: C,
77.6; H, 5.85; N, 4.79. IR 7KBr, n 7cm21)) 3336, 2953,
4.2.5.
porphyrin /5). A solution of 2,5-bis7phenyl hydroxy-
methyl)thiophene 7100 mg, 0.337 mmol), 4-iodo-
5,10-Diphenyl-15,20-bis/4-iodophenyl)-21-thia-
2861, 1110, 715. UV±Vis 7lmax 7nm), 1 7dm3 mol21 cm21
)
429 783,470), 513 77638), 547 7225), 616 71037), 678
71441).
benzaldehyde 7156 mg, 0.675 mmol) and pyrrole 770 ml,
1.013 mmol) in 25 ml of CHCl3 was treated with
BF3´O7Et)2 766 ml of 2.5 M stock solution, 3.3 mM). After
1 h, DDQ 7150 mg, 0.663) was added and stirring was
continued for additional 1 h. Chromatography with pet
ether/CH2Cl2 71:1) gave purple compound, 5 753 mg,
4.2.8. 5,10-Diphenyl-15,20-bis/4-formylphenyl)-21-thia-
porphyrin /8). The acetal group in 7 was hydrolyzed to
give the formyl substituted porphyrin 8. The acetal
porphyrin 7 750 mg, 0.0581), tri¯uoroacetic acid 77 ml),
10% aqueous sulfuric acid 72 ml) in 20 ml CH2Cl2 was
re¯uxed for 7 h. The deprotection was monitored by tlc.
The reaction mixture was cooled to room temperature and
poured into water. The organic layer was washed succes-
sively with water, aqueous sodium bicarbonate and brine
and dried over anhydrous sodium sulfate. The solvent was
removed and the residue was dissolved in CH2Cl2. Column
chromatography on silica with CH2Cl2 gave 8 as a dark
1
17%). H NMR 7CDCl3, d in ppm) 22.75 7s, 1H, NH),
7.82 7m, 6H, Ar), 7.91 7m, 4H, Ar), 8.13 7m, 4H, Ar),
8.25 7m, 4H, Ar), 8.58 7d, 2H, Jˆ4.5 Hz, b-pyrrole), 8.70
7d, 2H, Jˆ4.5 Hz, b-pyrrole), 8.93 7d, 2H, Jˆ4.5 Hz, b-pyr-
role), 9.77 7s, 2H, b-thiophene). FAB-MS C44H27N3SI2
calcd mass 883.0, obsd. m/z 884. Anal. calcd: C, 59.8; H,
3.07; N, 4.77. Found: C, 60.5; H, 3.01; N, 4.63. UV±Vis
7lmax 7nm), 1 7dm3 mol21 cm21)) 430 7424,000), 513
726,420), 548 77340), 618 73300), 679 74920).
1
purple solid in 65% yield 725 mg). H NMR 7CDCl3, d in
ppm) 22.73 7s, 1H, NH), 7.81 7m, 6H, Ar), 8.23 7m, 4H,

5354
D. Kumaresan et al. / Tetrahedron 58 %2002) 5347±5356
Ar), 8.27 7AA0BB0, 4H, Ar), 8.38 7AA0BB0, 4H, Ar), 8.54
7d, 2H, Jˆ2.4 Hz, b-py), 8.72 7d, 2H, Jˆ2.4 Hz, b-pyrrole),
8.89 7m, 2H, b-pyrrole), 9.79 7s, 2H, b-thiophene). FAB-
MS C46H29N3O2S calcd mass 687.2, obsd. m/z 688. Anal.
calcd: C, 83.7; H, 4.43; N, 6.36. Found: C, 82.8; H, 4.37; N,
6.19. IR 7KBr, n 7cm21)) 3325, 2934, 2852, 1704, 720. UV±
Vis 7lmax 7nm), 1 7dm3 mol21 cm21)) 431 743,924), 514
74233), 549 71388), 618 7614), 678 7853).
4.2.12. 5,10-Diphenyl-15,20-bis/3-ethynylphenyl)-21-oxa-
porphyrin /12). Compound 11 746 mg, 0.0694 mmol) was
dissolved in 12 ml of THF. K2CO3 750 mg, 0.361 mmol) in
3 ml of CH3OH was added and re¯uxed for 6 h. Chromato-
graphy on silica using CH2Cl2/CH3OH 797:3) afforded 12 as
1
a purple solid 738 mg, 82%). H NMR 7CDCl3, d in ppm)
3.20 7s, 2H, CCH), 7.75 7m, 8H, Ar), 7.91 7m, 2H, Ar), 8.18
7m, 6H, Ar), 8.32 7s, 2H, Ar), 8.57 7m, 4H, b-pyrrole), 8.86
7m, 2H, b-pyrrole), 9.20 7s, 2H, b-furan). FAB-MS
C48H29N3O calcd mass, 663.2, obsd. m/z 664. Anal. calcd:
C, 86.8; H, 4.40; N, 6.35. Found: C, 85.9; H, 4.39; N, 6.18.
UV±Vis 7lmax 7nm), 1 7dm3 mol21 cm21)) 421 7171,856),
443 733,833), 507 716,747), 538 74930), 612 72716), 674
72456).
4.2.9. 5,10-Diphenyl-15,20-bis {4-[2-/trimethylsilyl)-
ethynyl]phenyl}-21-oxaporphyrin /9). A solution of 2,5-
bis7phenyl hydroxymethyl)furan 7600 mg, 2.126 mmol), 4-
[2-7trimethylsilyl)ethynyl]benzaldehyde 7860 mg, 4.253
mmol) and pyrrole 7442 ml, 6.364 mmol) in 300 ml CHCl3
was treated with BF3´O7Et)2 7396 ml of 2.5 M stock solution,
3.3 mM). After 1 h, DDQ 7721 mg, 3.189 mmol) was added.
Chromatography on silica with CH2Cl2/CH3OH 797:3) gave
a purple solid 7270 mg, 15%). 1H NMR 7CDCl3, d in ppm)
0.38 7s, 18H, CH3), 7.78 7m, 6H, Ar), 7.88 7m, 4H, Ar), 8.12
7d, 4H, Jˆ6.5 Hz, Ar), 8.20 7d, 4H, Jˆ6.5 Hz, Ar), 8.65 7bs,
4H, b-pyrrole), 8.86 7s, 2H, b-pyrrole), 9.25 7s, 2H,
b-furan). FAB-MS C54H45N3OSi2 calcd mass 807.3, obsd.
m/z 808. Anal. calcd: C, 80.1; H, 5.61; N, 5.19. Found: C,
79.6; H, 5.39; N, 5.09. IR 7KBr, n 7cm21)) 3052, 2940,
2154, 705. UV±Vis 7lmax 7nm), 1 7dm3 mol21 cm21)) 423
7140,565), 508 719,964), 540 76752), 614 73828), 675
74253).
4.2.13. 5,10-Diphenyl-15,20-bis/4-iodophenyl)-21-oxa-
porphyrin /13). Samples of 2,5-bis7phenyl hydroxy-
methyl)furan 7100 mg, 0.357 mmol), 3-iodobenzaldehyde
7165 mg, 0.714 mmol) and pyrrole 774 ml, 1.071 mmol) in
CHCl3 750 ml) was treated with BF3´O7Et)2 766 ml of 2.5 M
stock solution, 3.3 mM). After 1 h, DDQ 7121 mg,
0.535 mmol) was added. Chromatography on silica with
CH2Cl2/CH3OH 794:6) gave purple solid, 13 743 mg,
1
14%). H NMR 7CDCl3, d in ppm) 7.79 7m, 6H, Ar), 7.93
7m, 4H, Ar), 8.12 7AA0BB0, 4H, Ar), 8.22 7AA0BB0, 4H,
Ar), 8.72 7bs, 4H, b-pyrrole), 8.87 7m, 2H, b-pyrrole), 9.33
7s, 2H, b-furan). FAB-MS C44H27N3OI2 calcd mass, 867.0,
obsd. m/z 868. Anal. calcd: C, 60.9; H, 3.13; N, 4.84. Found:
C, 61.5; H, 3.34; N, 4.67. IR 7KBr, n 7cm21)) 3052, 2940,
715. UV±Vis 7lmax 7nm), 1 7dm3 mol21 cm21)) 423
7205,404), 443 753,560), 507 725,896), 539 75195), 614
73347), 674 74338).
4.2.10. 5,10-Diphenyl-15,20-bis/4-ethynylphenyl)-21-oxa-
porphyrin /10). Compound 9 7100 mg, 0.124 mmol) was
dissolved in 20 ml THF and K2CO3 7171 mg, 1.237 mmol)
in CH3OH 76 ml) was added to it. The reaction mixture was
re¯uxed for 8 h. Chromatography on silica with CH2Cl2/
1
CH3OH 797:3) gave purple solid, 10 770 mg, 85%). H
4.2.14. 5,10-Diphenyl-15,20-bis/3-iodophenyl)-21-oxa-
porphyrin /14). A solution of 2,5-bis7phenyl hydroxy-
methyl) furan 7100 mg, 0.357 mmol), meta-iodo-
benzaldehyde 7165 mg, 0.714 mmol) and pyrrole 774 ml,
1.071 mmol) in CHCl3 750 ml) was treated with
BF3´O7Et)2 766 ml of 2.5 M stock solution, 3.3 mM). After
1 h, DDQ 7121 mg, 0.535 mmol) was added. Chromato-
graphy on silica with CH2Cl2/CH3OH 794:6) gave purple
NMR 7CDCl3, d in ppm) 3.31 7s, 2H, CCH), 7.79 7m, 6H,
Ar), 7.89 7m, 4H, Ar), 8.17 7m, 8H, Ar), 8.55 7d, 2H,
Jˆ4.5 Hz, b-pyrrole), 8.59 7d, 2H, Jˆ4.5 Hz, b-py), 8.85
7s, 2H, b-pyrrole), 9.20 7s, 2H, b-furan). FAB-MS
C48H29N3O calcd mass 663.2, obsd. m/z 664. Anal. calcd:
C, 86.8; H, 4.40; N, 6.35. Found: C, 86.3; H, 4.32; N, 6.09.
IR 7KBr, n 7cm21)) 3242, 2115, 702. UV±Vis 7lmax 7nm), 1
7dm3 mol21 cm21)) 422 7330,119), 508 733,805), 540
77664), 614 74539), 675 75931).
1
solid, 14 734 mg, 11%). H NMR 7CDCl3, d in ppm) 7.58
7t, 2H, Jˆ3.6 Hz Ar), 7.89 7m, 6H, Ar), 8.20±8.39 7m, 8H,
Ar), 8.65 7s, 2H, Ar), 8.85 7s, 2H, b-pyrrole), 9.07 7m, 4H,
b-pyrrole), 9.64 7s, 2H, b-furan). FAB-MS C44H27N3OI2
calcd mass 867.0, obsd. m/z 868. Anal. calcd: C, 60.9; H,
3.13; N, 4.84. Found: C, 61.1; H, 3.42; N, 4.58. IR 7KBr, n
4.2.11. 5,10-Diphenyl-15,20-bis {3-[2-/trimethylsilyl)-
ethynyl]phenyl}-21-oxaporphy-rin /11). Samples of 2,5-
bis7phenyl hydroxymethyl)furan 7100 mg, 0.357 mmol), 3-
[2-7trimethylsilyl)ethynyl]benzaldehyde 7144 mg, 0.714
mmol) and pyrrole 774 ml, 1.071 mmol) in 50 ml CHCl3
were condensed in the presence of BF3´O7Et)2 766 ml of
2.5 M stock solution, 3.3 mM). After 1 h, DDQ 7121 mg,
0.535 mmol) was added and stirred for an additional 1 h.
Chromatography on silica using CH2Cl2/CH3OH 797:3)
7cm21)) 2924, 2853, 705. UV±Vis 7lmax 7nm),
1
7dm3 mol21 cm21)) 421 7119,667), 507 714,750), 538
73434), 613 72205), 674 72241).
4.2.15. 5,10-Diphenyl-15,20-bis[4-/5,5-dimethyl-1,3-dioxa-
cyclohex-2-yl)phenyl]-21-oxaporphyrin /15). A solution
of 2,5-bis7phenyl hydroxymethyl)furan 7500 mg, 1.784
mmol), 2-75,5-dimethyl-1,3-dioxacyclohex-2-yl)benzlade-
hyde 7825 mg, 3.74 mmol) and pyrrole 7373 ml,
5.353 mmol) were dissolved in 25 ml of CHCl3 and stirred
at room temperature under argon for 10 min. Tri¯uoroacetic
acid 71 ml, 0.0130 mmol) was added to initiate the conden-
sation and the reaction mixture was stirred for 1 h under
argon atmosphere. DDQ 7635 mg, 2.797 mmol) was then
added and the reaction mixture was stirred for an additional
1 h in air. The solvent was removed in vacuo and the crude
1
gave purple solid, 11 729 mg, 10%). H NMR 7CDCl3, d
in ppm) 0.39 7s, 18H, CH3), 7.68 7t, 2H, Jˆ6 Hz, Ar), 7.79
7m, 6H, Ar), 7.89 7d, 2H, Jˆ4 Hz, Ar), 8.10 7d, 2H, Jˆ4 Hz,
Ar), 8.19 7d, 4H, Jˆ4 Hz, Ar), 8.31 7s, 2H, Ar), 8.57 7m, 4H,
b-pyrrole), 8.85 7s, 2H, b-pyrrole), 9.20 7s, 2H, b-furan).
FAB-MS C54H45N3Si2O calcd mass, 807.3, obsd. m/z 808.
Anal. calcd: C, 80.1; H, 5.61; N, 5.19. Found: C, 79.3; H,
5.90; N, 5.42. UV±Vis 7lmax 7nm), 1 7dm3 mol21 cm21))
423 7128,567), 444 746,728), 507 718,110), 538 73687),
612 72601), 673 72753).

D. Kumaresan et al. / Tetrahedron 58 %2002) 5347±5356
5355
compound was loaded on silica and eluted with CH2Cl2. The
desired compound moved as a second band with CH2Cl2/5%
CH3OH to afford purple solid, 15 in 5% yield. 775 mg). H
4.65; N, 7.79. IR 7KBr, n 7cm21)) 2925, 2855, 1555, 711.
UV±vis 7lmax 7nm), 1 7103 dm3 mol21 cm21)) 432 7233.4),
515 7110.9), 619 72.58), 679 74.45).
1
NMR 7CDCl3, d in ppm) 1.46 7s, 12H, CH3), 3.85 7d, 4H,
Jˆ6.6 Hz, CH2), 3.96 7d, 4H, Jˆ6.6 Hz, CH2), 5.75 7s, 2H,
CH), 7.77 7m, 6H, Ar), 7.90 7m, 4H, Ar), 8.19 7m, 8H, Ar),
8.56 7d, 2H, Jˆ4.5 Hz, b-pyrrole), 8.65 7d, 2H, Jˆ4.5 Hz,
b-pyrrole), 8.85 7m, 2H, b-pyrrole), 9.20 7s, 2H, b-furan).
FAB-MS C56H49N3O5 calcd mass 843.3, obsd. m/z 844.
Anal. calcd: C, 79.7; H, 5.85; N, 4.98. Found: C, 79.1; H,
5.94; N, 4.89. IR 7KBr, n 7cm21)) 2924, 2850, 1103, 711.
UV±Vis 7lmax 7nm), 1 7dm3 mol21 cm21)) 421 7112,761),
507 716,380), 539 75776), 612 73982), 673 73349).
4.2.18. /BDPY)2OTPPH /18). Samples of 12 710 mg,
0.0151 mmol), BDPY-I 720.7 mg, 0.0527 mmol) and
AsPh3 711 mg, 0.0361 mmol) were dissolved in 12 ml of
toluene/triethylamine 75:1) and purged argon for 15 min.
Pd27dba)3 74.1 mg, 0.00452 mmol) was added and reaction
mixture was stirred at 358C under argon for 3 h. The solvent
was removed in vacuo and the crude compound was loaded
on silica column and eluted with dichloromethane. The
excess BDPY-I, AsPh3 and other side products were
removed and the desired compound was then eluted with
CH2Cl2/ethyl acetate 785:15). The compound was then
passed through a size exclusion chromatography with
toluene and recrystallized with CH2Cl2/CH3OH to afford
18 as a reddish compound in 17% yield 73.2 mg). 1H
NMR 7CDCl3, d in ppm) 1.25 7s, 12H, CH3), 6.35 7m, 4H,
BDPY pyrrole), 6.70 7m, 4H, BDPY pyrrole), 7.48 7m, 4H,
Ar), 7.67 7m, 4H, Ar), 7.78 7m, 8H, Ar), 7.99 7m, 2H, Ar),
8.21 7m, 6H, Ar), 8.42 7s, 2H, Ar) 8.65 7d, 2H, Jˆ4.5 Hz,
b-pyrrole), 8.93 7s, 2H, b-pyrrole), 9.22 7s, 2H, b-furan).
FAB-MS C82H55N7OB2F4 calcd mass 1251.4, obsd. m/z
1251. Anal. calcd: C, 78.6; H, 4.42; N, 7.86. Found: C,
77.8; H, 4.35; N, 7.78. IR 7KBr, n 7cm21)) 2922, 2848,
1556, 705. UV±vis 7lmax 7nm), 1 7103 dm3 mol21 cm21))
443 734.2), 425 7180.5), 515 7150.2), 611 73.89), 673 73.89).
4.2.16. 5,10-Diphenyl-15,20-bis/4-formylphenyl)-21-oxa-
porphyrin /16). The acetal porphyrin 15 750 mg, 0.05924),
tri¯uoroacetic acid 77 ml), 10% aqueous sulfuric acid 72 ml)
in 20 ml CH2Cl2 was re¯uxed for 7 h. The deprotection was
monitored with tlc. The reaction mixture was cooled to
room temperature and poured into water. The organic
layer was washed successively with water, aqueous sodium
bicarbonate and brine and dried over anhydrous sodium sul-
fate. The solvent was removed and the residue was
dissolved in CH2Cl2. Column chromatography on silica
with CH2Cl2 gave purple solid, 16 in 55% yield 722 mg).
1H NMR 7CDCl3, d in ppm) 7.81 7m, 6H, Ar), 8.23 7m, 4H,
Ar), 8.29 7m, 4H, Ar), 8.39 7m, 4H, Ar), 8.61 7d, 4H,
Jˆ4.5 Hz, b-pyrrole), 8.81 7m, 2H, b-pyrrole), 9.26 7s,
2H, b-furan), 10.38 7s, 2H, CHO). FAB-MS C46H29N3O3
calcd mass 671.2, obsd. m/z 672. Anal. calcd: C, 82.2; H,
4.35; N, 6.25. Found: C, 82.8; H, 4.25; N, 6.18. IR 7KBr, n
7cm21)) 2927, 2841, 1703, 702. UV±Vis 7lmax 7nm), 1
7dm3 mol21 cm21)) 420 7109,761), 509 714,581), 539
75423), 611 73889), 672 73257).
Acknowledgements
This research was supported by Department of Atomic
Energy 7No. 2001/37/21/BRNS/797) and Department of
Science and Technology, Government of India, New
Delhi. Mass spectra were obtained at CDRI, Lucknow and
NMR were obtained at RSIC, IIT-Bombay.
4.2.17. /BDPY)2STPPH /17). Samples of 2 728 mg,
0.0412 mmol) and BDPY-I 776 mg, 0.1935 mmol) were
dissolved in 36 ml of toluene/triethylamine 75:1). AsPh3
728 mg, 0.0918 mmol) was then added and the solution
was deaerated with argon for 15 min. A catalytic amount
of Pd27dba)3 712 mg, 0.0132 mmol) was added to initiate the
coupling reaction. The reaction mixture was stirred at 358C
under argon for 3 h. The reaction was monitored with tlc at
regular intervals and the reaction was stopped after the
consumption of 2. The solvent was removed on rotary
evaporator under reduced pressure and the crude material
was dissolved in CH2Cl2 and passed through short silica
column using CH2Cl2 as solvent to remove the palladium
species, triphenylarsine, excess BDPY-I and other side
products. The compound was then passed through size
exclusion chromatography with toluene to remove any
undesired high molecular weight materials. The compound
with very small amounts of impurities was passed through
silica column using pet ether/CH2Cl2 71:1) to afford the
References
1. 7a) Ravikanth, M.; Chandrashekar, T. K. Struct. Bond. 1995,
82, 105±188 and references cited there in. 7b) Latos-
Grazynski, L.; Olmstead, M. M.; Balch, A. L. Chem. Eur. J.
1997, 3, 268±278. 7c) Gross, Z.; Saltsman, I.; Pandian, R. P.;
Barzilay, C. M. Tetrahedron Lett. 1997, 38, 2383±2386.
2. 7a) Latos-Grazynski, L.; Lisowski, J.; Olmstead, M. M.;
Balch, A. L. Inorg. Chem. 1989, 28, 1183±1188. 7b) Latos-
Grazynski, L.; Lisowski, J.; Olmstead, M. M.; Balch, A. Inorg.
Chem. 1989, 28, 3328±3331. 7c) Chmielewski, P.;
Grzeszczuk, M.; Latos-Grazynski, L.; Lisowski, J. Inorg.
Chem. 1989, 28, 3546±3552. 7d) Latos-Grazynski, L.;
Pacholska, E.; Chmielewski, P. J.; Olmstead, M. M.; Balch,
A. L. Inorg. Chem. 1996, 35, 566±573. 7e) Latos-Grazynski,
L.; Pacholska, E.; Chmielewski, P. J.; Olmstead, M. M.;
Balch, A. L. Angew. Chem., Int. Ed. Engl. 1995, 34, 2252±
2254. 7f) Pandian, R. P.; Chandrashekar, T. K. J. Chem. Soc.,
Dalton Trans. 1993, 119±125.
1
reddish product in 28% yield 715 mg). H NMR 7CDCl3,
d in ppm) 22.69 7s, 1H, NH), 1.25 7s, 12H, CH3), 6.32
7d, 4H, Jˆ4.5 Hz, BDPY pyrrole), 6.78 7d, 4H, Jˆ4.5 Hz,
BDPY pyrrole), 7.57 7d, 4H, Jˆ4 Hz, Ar), 7.79 7m, 10H,
Ar), 7.96 7d, 4H, Jˆ4 Hz, Ar), 8.25 7m, 8H, Ar), 8.68 7d, 2H,
Jˆ4.5 Hz, b-pyrrole), 8.72 7d, 2H, Jˆ4.5 Hz, b-pyrrole),
8.98 7s, 2H, b-pyrrole), 9.77 7s, 2H, b-thiophene). FAB-
MS C82H55N7SB2F4 calcd mass 1267.4, obsd. m/z 1268.
Anal. calcd: C, 77.7; H, 4.37; N, 7.73. Found: C, 78.1; H,
3. 7a) Latos-Grazynski, L.; Olmstead, M. M.; Balch, A. L. Chem.
Eur. J. 1997, 3, 268±278. 7b) Sridevi, B.; Narayanan, S. J.;
Srinivasan, A.; Chandrashekar, T. K. J. Chem. Soc., Dalton
Trans. 1998, 1979±1984. 7c) Sridevi, B.; Narayanan, S. J.;

5356
D. Kumaresan et al. / Tetrahedron 58 %2002) 5347±5356
Srinivasan, A.; Reddy, M. V.; Chandrashekar, T. K.
J. Porphyrins Phthalocyanines 1998, 2, 69±78.
8. 7a) Ravikanth, M.; Strachan, J.-P.; Li, F.; Lindsey, J. S.
Tetrahedron 1998, 54, 7721±7734. 7b) Syper, L. Tetrahedron
Lett. 1966, 4493±4498. 7c) Cho, H. S.; Jeong, D. H.; Yoon,
M.-C.; Kim, Y. H.; Kim, Y.-R.; Kim, D.; Jeoung, S. C.; Kim,
S. K.; Aratani, N.; Shinmori, H.; Osuka, A. J. Phys. Chem. A
2001, 105, 4200±4210.
4. 7a) Ravikanth, M. Tetrahedron Lett. 2000, 41, 3709±3712.
7b) Kumaresan, D.; Agarwal, N.; Ravikanth, M. J. Chem.
Soc., Perkin Trans. 1 2001, 1644±1648. 7c) Ravikanth, M.;
Agarwal, N.; Kumaresan, D. Chem. Lett. 2000, 836±837.
5. 7a) Ravikanth, M. Chem. Lett. 2000, 480±481. 7b) Kumaresan,
D.; Santra, S.; Ravikanth, M. Synlett 2001, 1635±1637.
6. 7a) Kumaresan, D.; Gupta, I.; Ravikanth, M. Tetrahedron Lett.
2001, 42, 8547±8550. 7b) Cho, W-S.; Kim, H.-J.; Littler, B. J.;
Miller, M. A.; Lee, C.-H.; Lindsey, J. S. J. Org. Chem. 1999,
64, 7890±7901.
9. 7a) Wagner, R. W.; Johnson, T. E.; Li, F.; Lindsey, J. S. J. Org.
Chem. 1995, 60, 5266±5273. 7b) Ravikanth, M. Ind. J. Chem.
A 2001, 40A, 86±89.
10. Li, F.; Yang, S.-I.; Ciringh, Y.; Seth, J.; Martin, III, C. M.;
Singh, D. L.; Kim, D.; Birge, R. R.; Bocian, D. F.; Holten, D.;
Lindsey, J. S. J. Am. Chem. Soc. 1998, 120, 10001±10017.
7. Ulman, A.; Manassen, J. J. Am. Chem. Soc. 1975, 97, 6540±
6544.